Icariside II is a known compound; its structure is as follows:

It is reported that icariside II has a skin whitening effect (WO2008/035918).
The male sexual function is consisted by a series of events, including the penile erection with blood hemodynamic changes taking place in the erectile tissue of corpus cavernosum under the regulation of nervous system during sexual stimulation. Firstly, with sexual stimulation or sexual desire, the function of corpus cavernosum was controlled by the efferent nerve from the pelvic nerve, under the central regulation of erectile regulation center in brain and spinal cord. The parasympathetic nerve ending of the efferent nerve releases acetylcholine, which activates endothelial nitric oxide synthase (eNOS) in endothelial cells to promote nitric oxide (NO) generation, meanwhile, nNOS from non-adrenanic non-cholinergic (NANC) nerve promote NO generation. NO activates soluble guanylate cyclase (sGC) in the smooth muscle cells to promote cGMP synthesis. cGMP activating protein G (PKG) and the intracellular calcium is decreased to induce smooth muscle relaxation. Then penis cavernosal artery dilation and cavernous sinus expanding are induced for increasing the arterial blood perfusion in the corpus cavernosum and the vein under the albuginea is pressed by expanded corpus cavernosm, thereby blocking the venous outflow from corpus cavernosm induce penile erection. cGMP could be regulated by cGMP specific phosphodiesterase type V (PDE5) to lose activity. The increase of sympathetic nerve activity leads to contraction of smooth muscle, which turns to flaccid status. Therefore, erectile response depends on the integrity of neural structure and function, corpus cavernosum smooth muscle, endothelial cell structure, and regulated by NO-cGMP signaling pathway.
With the advance of modern science and technology, it had been identified that more than 50% of sexual dysfunction patients suffered from spinal cord and brain peripheral nerve injury, hypertension, atherosclerosis, and diabetes etc. In addition, these diseases caused penile corpus cavernosum nerve injury, and dysfunction of smooth muscle and endothelial cells of penile corpus cavernosum. Studies show that organic erectile dysfunction caused by diabetes, hypertension, atherosclerosis, nerve damage and other diseases is related to the pathological changes on penile corpus cavernous nerve, corpus cavernosum smooth muscle and endothelial cell, while the molecular biology study showed a significantly lower levels of NOS activity or gene expression in corpus cavernosum is closely related to those conditions.
Although the oral agent phosphodiesterase (PDE5) inhibitor, such as sildenafil, showed a reliable one time effects for treating erectile dysfunction on demanded, if it is taken before sexual activity, but it showed no effects in more than 20% of patients with severe organic erectile dysfunction. In addition, PDE5i showed no therapeutic effect on the pathological changes to the erectile tissue of penis. Meanwhile, it caused varying degrees of side effects such as flushing, headache, visual disturbances, low blood pressure and back pain, etc. More importantly, it has potentially risk in patients with cardiovascular disease and is strictly inhibited from co-administration with nitrite. Actually, intracavernous injection of vascular relaxation drugs such as paparvarin, phentolamine or prostaglandin E1 etc is also used for treating erectile dysfunction. However, this therapy had no effect on more than 20% of patients with severe organic erectile dysfunction, and also showed no therapeutic effect on the pathophysiological changes to the penis of erectile dysfunction. Meanwhile, it caused side effects such as lower the blood pressure, headache and dizziness, local pain, persistent penile erection, penile fibrosis. The clinical application of intracavernous injection therapy is often prohibited.
Therefore, a new medication with a potential for preventing and treating erectile dysfunction and with therapeutic effects on pathological change to penile corpus cavernosm, such as promoting nerve regeneration, regulating the function of corpus cavernosum smooth muscle and endothelial cell and regulating NOS activity or gene expression, is highly desired clinically. However, there is no such a prevention and treatment drug by now.
Epimedium herb is used in traditional medicine and often served as the prescription strong tonic ingredient, but the mechanisms have not been clarified. Recent studies have shown that Epimedium contains many active ingredients, such as icariin, icariside I, icariside II, volatile oil, wax alcohol, alkanes, phytosterols, tannins, linoleic acid and so on. Also, some traces of magnoflorin, epimedoside A, epimedin A, B, C, querecetin, and anhydroicariin-3-O-rhamnoside were isolated recently. Icariside II is currently used as standard chemical reagent in laboratory. Previous study found that icariside II could selectively inhibit PDE5, but its PDE5 inhibiting potency is significantly lower than sildenafil when tested in vitro. The initial clinical trial in volunteers (with informed consent) with erectile dysfunction showed that a single oral administration of icariside II (500 mg/time) before sexual activity caused some improvement on erectile function, but the effect is not significant. These results indicated that icariside II have a weak potency in inhibiting PDE5 activity. A single oral administration of icariside II before sexual activity is not sufficient to treat erectile dysfunction as sildenafil.